The field of the disclosure is directed to superconducting quantum circuits and devices. More particularly, the disclosure is directed to systems and methods related to quantum information processing and quantum computation.
Superconducting integrated circuits are finding increased use in a variety of applications. For instance, in the field of quantum computation, the performance of superconducting quantum bits (“qubits”) has advanced rapidly in recent years, with preliminary multi-qubit implementations leading toward scalable, surface code architectures. In contrast to classical computational methods that rely on binary data stored in the form of definite on/off states, or bits, methods in quantum computation take advantage of the quantum mechanical nature of superconducting quantum systems, which may be represented using a superposition of multiple quantum states.
However, maintaining a superposition state is challenging for practical implementations. This is because various sources of noise induce a loss of quantum ordering, or coherence in the phase angles between the different components of the system in quantum superposition. Such dephasing makes the realization of quantum computers difficult, since sufficient preservation of coherent quantum states is required in order to perform useful computation. For superconducting qubits, low-frequency magnetic flux noise is a dominant source of dephasing, resulting in appreciable errors when implemented in large-scale circuits. In addition, the magnitude of flux noise is roughly universal across various different device materials and fabrication processes. Despite thirty years of research, there has been no successful demonstration of reducing this noise, placing severe limitations on progress in quantum information processing and quantum computation.
In general, during the fabrication process, superconducting devices are exposed to ambient atmospheric surroundings for extended periods of time. Subsequently, in operation, the superconducting devices are cooled to low temperatures, typically using vacuum cryostats that maintain poor background pressure, allowing the adsorption of a high density of magnetically active defects. Such defects can produce low-frequency magnetic flux noise that leads to strong dephasing. In the case of qubit devices, some efforts to avoid magnetic flux noise have been made by operating the devices at fixed frequencies where the qubit is insensitive to first order to magnetic flux fluctuations. However, such implementations severely constrain the architectures of multi-qubit circuits and make scaling to larger systems a major challenge.
In light of the above, there remains a need for novel approaches that address noise sources affecting superconducting integrated circuits.